1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile, and a multi-function printer including a plurality of the functions, and more specifically to a configuration thereof including a plurality of fixing apparatuses fixing a toner image on a sheet.
2. Description of the Related Art
Hitherto, an image forming apparatus adopting an electro-photographic system or the like is configured to fix a toner image onto a sheet on which the toner image has been formed by heating and pressing the sheet in passing through a nip between a fixing roller and a pressure roller composing a fixing apparatus.
Because the surface roughness of the fixing roller affects the quality of the image formed on the sheet in such an image forming apparatus, an arrangement is made to roughen the surface of the fixing roller by a roughening roller to keep desirable surface roughness as disclosed in Japanese Patent Application Laid-open No. 2008-40363. Japanese Patent Application Laid-open No. 2008-40363 proposes to roughen the surface of the fixing roller to the desirable roughness by bringing the roughening roller rotated at a surface moving speed different from a surface moving speed of the fixing roller into contact with the fixing roller to imprint fine flaws on the surface of the fixing roller.
Japanese Patent Application Laid-open No. 2008-40363 restrains streaky gloss unevenness from being generated on an output image by widthwise both edge parts (referred to as ‘coba parts’ hereinafter) of a sheet passing through the nip, even if streaky flaws are imprinted on the surface of the fixing roller by the coba parts, by roughening the surface of the fixing roller to the desirable surface roughness.
However, in the fixing apparatus configured to bring the roughening roller into contact with the surface of the fixing roller to restrain such gloss unevenness caused by the coba parts, the fine flaws imprinted on the surface of the fixing roller by the roughening roller possibly generate fine gloss unevenness on the output image. It is possible to make such fine gloss unevenness inconspicuous by refining the flaws imprinted on the surface of the fixing roller. However, it is hard to suppress the gloss unevenness from being generated due to the coba parts if the flaws imprinted on the surface of the fixing roller are further made finer. Accordingly, it is desirable for an image forming apparatus required to output a high quality image to be able to suppress a drop in quality of the output image by suppressing the generation of the fine gloss unevenness in addition to the gloss unevenness caused by the coba parts.